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multicpu1sec-c: use plain POSIX instead of stdlib

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As it will be used every second, we should limit the overhead
This commit is contained in:
Steve Schnepp 2015-03-31 22:17:16 +00:00
parent 6ed404cbc9
commit 7d88587fb6
1 changed files with 27 additions and 17 deletions
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44
plugins/system/multicpu1sec/multicpu1sec-c.c
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@ -5,6 +5,7 @@
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <time.h>
@ -110,36 +111,45 @@ int acquire() {
time_t epoch = wait_until_next_second();
/* Reading /proc/stat */
FILE* f = fopen(PROC_STAT, "r");
// Read and ignore the 1rst line
char buffer[1024];
fgets(buffer, 1024, f);
int f = open(PROC_STAT, O_RDONLY);
const int buffer_size = 64 * 1024;
char buffer[buffer_size];
// whole /proc/stat can be read in 1 syscall
if (read(f, buffer, buffer_size) <= 0) {
return fail("cannot read " PROC_STAT);
}
// ignore the 1rst line
char* line;
const char* newl = "\n";
line = strtok(buffer, newl);
/* open the spoolfile */
FILE* cache_file = fopen(cache_filename, "a");
int cache_file = open(cache_filename, O_CREAT | O_APPEND | O_WRONLY);
/* lock */
flock(fileno(cache_file), LOCK_EX);
while (! feof(f)) {
if (fgets(buffer, 1024, f) == 0) {
// EOF
break;
}
flock(cache_file, LOCK_EX);
for (line = strtok(NULL, newl); line; line = strtok(NULL, newl)) {
// Not on CPU lines anymore
if (strncmp(buffer, "cpu", 3)) break;
if (strncmp(line, "cpu", 3)) break;
char cpu_id[64];
long usr, nice, sys, idle, iowait, irq, softirq;
sscanf(buffer, "%s %ld %ld %ld %ld %ld %ld %ld", cpu_id, &usr, &nice, &sys, &idle, &iowait, &irq, &softirq);
sscanf(line, "%s %ld %ld %ld %ld %ld %ld %ld", cpu_id, &usr, &nice, &sys, &idle, &iowait, &irq, &softirq);
long used = usr + nice + sys + iowait + irq + softirq;
fprintf(cache_file, "%s.value %ld:%ld\n", cpu_id, epoch, used);
char out_buffer[1024];
sprintf(out_buffer, "%s.value %ld:%ld\n", cpu_id, epoch, used);
write(cache_file, out_buffer, strlen(out_buffer));
}
fclose(cache_file);
fclose(f);
close(cache_file);
close(f);
}
}